Buly, this is just a 25 year auto technitions wealth of elect.  experience talking, when you are testing (an ongoing problem )  circuit I always test using the fobiden test LIGHT, checking to see  if that circuit Will carry power. Many times in the past I saw  other guys using an ohm meter that said the circuit was fine/ closed, put power on it and it went open, recheck with dig. meter  said ok again. Yes this is the digital age but, old world  technology still applies (sometimes).  If the circuit is for a  sensor , or ecu communication then I just isolate the circuit from  the computer to test if it will carry a load. Again this policy is  usually used on problem cars not the everyday easy diog. & repair.  But sometimes it catches me even on those.  Hope this helps.   David,  RV6A two more weeks till paint on fuselage.